The present invention pertains to methods of forming oxide regions of varying thickness over semiconductor substrates.
Semiconductor devices utilize oxide regions, such as silicon dioxide regions, for a variety of applications. For example, oxide regions may be used to form gate oxides. The thickness of the gate oxide can affect various electrical properties of the transistor structures incorporating the gate oxide.
It is often desirable to form gate oxides of different thickness on the same semiconductor substrate. For example, it is desirable to form DRAM devices utilizing a thick gate oxide in the array areas of the semiconductor substrate and to form periphery devices such as logic transistors utilizing a thin gate oxide in the periphery areas of the semiconductor substrate. However, conventional processing techniques are may not be suitable for the formation of high quality gate oxides of different thicknesses.
Thus, there remains a need in the art for methods of dual gate oxides having differing thicknesses. Additionally, there remains a need in the art for methods of forming dual gate oxides of a quality suitable for use in DRAM and other devices.
The present invention provides methods of forming gates oxides having varying thicknesses. A first gate oxide layer is generally formed over first and second areas of a semiconductor substrate. An oxynitride layer is formed over the first gate oxide layer. A portion of the oxynitride and first gate oxide layers overlying the second area of the semiconductor substrate is then removed. Finally, a second gate oxide layer is grown on the exposed second area of the semiconductor substrate, and a reoxidized first gate oxide is simultaneously formed. The reoxidized first gate oxide is thinner than the second gate oxide. The second gate oxide is suitable for use in memory devices of DRAM, and the reoxidized first gate oxide is suitable for use in the periphery devices of DRAM.
Accordingly, it is an object of the present invention to provide a method of forming dual gate oxides. Further, it is an object of the present invention to provide high quality gate oxides suitable for use in the array and periphery areas of DRAM devices. Additional objects and advantages of the present invention will become apparent from the subsequent drawings and detailed description of the preferred embodiments.